Arnold (1917:398) records this species nesting in hollow twigs of an acacia. The species has also been noted by the present author nesting in hollow twigs of cocoa in both Nigeria and Ghana, and in the former nests are also made in twigs on small shrubs as well as high up in larger trees. (Bolton 1974)
- 1 Identification
- 2 Distribution
- 3 Biology
- 4 Castes
- 5 Nomenclature
- 6 References
A member of the tenuis group. There is a possibility that some specimens of Cataulacus pygmaeus may be confused with Cataulacus brevisetosus as the clypeal and cephalic hairs in the former are occasionally thickened from base to apex and under low magnification may appear clavate. In these cases the identity of the specimen may be confirmed by mensurable characters, as the head in pygmaeus is usually broader (CI 94 - 97) than in specimens of brevisetosus with approximately similar head length, whilst the eyes are always relatively smaller, OI 41 - 46, as opposed to OI 49 - 54 in brevisetosus. Other absolute measurements will also give an indication of identity as only the largest brevisetosus individuals overlap the smallest pygmaeus workers in size. Also, the rugoreticulum on the pronotal dorsum is usually more coarse and more widely spaced in pygmaeus and the interspaces of this sculpturation tend to be less strongly punctate and are usually distinctly glossy. (Bolton 1974)
Keys including this Species
Distribution based on Regional Taxon Lists
Distribution based on AntMaps
Distribution based on AntWeb specimens
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Much of the information concerning the biology of Cataulacus species is anecdotal and fragmentary. Arnold (1917) wrote a succinct general overview of Cataulacus biology that still remains quite informative. Arnold reports "all the species of this genus are tree-ants, usually forming medium sized nests in hollow twigs and stems, or more rarely, under the bark. They are timid and slow-moving insects, often feigning death or dropping rapidly to the ground when disturbed. As Bingham has remarked in connection with this genus (Fauna Brit. India, Formicidae), these ants have the habit of wandering over the trunks of trees and the leaves in what appears to be a very aimless and languid manner. I have occasionally seen them breaking open the earthen tunnels constructed by termites over the trunks of trees and attack the inmates."
Bolton (1974) expands upon this earlier account - "All known Cataulacus species are arboreal or subarboreal nesters and they predominantly forage on the trees and shrubs in which the nests are situated. Very few appear to come down to ground level but in West Africa the small species Cataulacus pygmaeus and Cataulacus brevisetosus may be found foraging in leaf litter or crossing the ground to ascend a tree other than the one in which the nest is situated. The nests themselves are usually constructed in small hollow twigs or stems by the smaller species and in rotten branches or rotted portions of the tree trunk by the larger species. This is rather a generalization as some small species are known which nest in and under rotten bark (e.g. Cataulacus vorticus) and undoubtedly some of the larger forms will eventually be found inhabiting relatively small cavities in plants.
Various species of the genus in Africa are known to inhabit a variety of galls, acacias and bushes as well as large trees. Numerous species have been found nesting in, and have therefore been often collected from, cocoa in Africa. Some of these species are Cataulacus guineensis, Cataulacus pygmaeus, Cataulacus mocquerysi, Cataulacus egenus, Cataulacus vorticus, Cataulacus brevisetosus, Cataulacus kohli and Cataulacus theobromicola. Feeding habits in the genus are mostly unknown but the present author has noted C. guineensis tending aphids and small coccids.
On the plants ants of the genus Cataulacus often occur together with Oecophylla or species of Crematogaster, and appear to be mostly tolerated (at least they are not evicted) by the majority of these forms. Their defence against attackers of these genera lies primarily in their armoured exterior, but their ultimate escape reaction is to curl up and release their grip on the plant, falling to the ground and thus making their escape. The decision to remain immobile and present an armoured surface or to drop from the plant appears to depend upon the size or persistence of the aggressor; larger attackers usually precipitate the latter reaction, but it has also been noted as a result of persistent and unwanted attention by a series of workers of a small Crematogaster species.
The majority of species are forest-dwelling forms, with relatively few adapted to savannah or veldt conditions. Those which do, however, occur in these zones tend to be very successful in their chosen habitat and often possess a wide distribution. A few species are apparently able to exist in any region of Africa providing the basic essentials of nesting-site and food supply are met with, but on the whole the fauna may be divided into forest and non-forest forms."
Some species have nests that can be protected by a single worker's head, as its shape matches the nest entrance and forms an effective plug.
It has more recently been discovered that some species of Cataulacus are efficient gliders (Cataulacus erinaceus, Cataulacus guineensis, Cataulacus mocquerysi and Cataulacus tardus). Workers exhibit directed movement while in freefall that allows them to glide back to regain a hold on the same tree trunk. (Yanoviak et al. 2005, 2007, 2008)
The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- brevisetosus. Cataulacus brevisetosus Forel, 1901d: 305 (w.) ANGOLA. [Also described as new by Forel, 1903e: 560.] Subspecies of pygmaeus: Santschi, 1916b: 508; Wheeler, W.M. 1922a: 298. Revived status as species: Santschi, 1939b: 246; Bolton, 1974a: 31. Senior synonym of meduseus and material of the unavailable name plebeja referred here: Bolton, 1974a: 31.
- meduseus. Cataulacus meduseus Santschi, 1939b: 245 (w.) SOUTH AFRICA. Junior synonym of brevisetosus: Bolton, 1974a: 31.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Bolton (1974) - The interrelationships and the constituent species of the complex centring on brevisetosus are difficult to decide owing to the great variation in details of sculpturation and shape met with in individuals. The great majority of the forms included in the synonymy were originally separated from one another only on minor details of head shape, petiole node shape, lengths of propodeal spines and variation in size, all of which characters are very variable, often between individuals of the same colony. Workers from each end of the size range of a series collected at Adeiso, Ghana by D. Leston would earlier this century probably have been described as separate varieties or subspecies if collected singly. The size range between the largest and smallest workers in this series is HL 0.76 – 1.00, HW 0.68 – 0.90, (CI 89 - 90), EL 0.36 – 0.44, (OI 49 - 51), PW 0.54 – 0.70, AL 0.74 – 1.04; coupled with which are some variations in sculpturation and in shape. Because of this variability it is probable that some very closely related forms may be present in the species now called brevisetosus, but which are not recognizable as separate as the amount of material available at present is not great enough to show up any consistent characters which they may have. A reassessment of all the forms now placed in brevisetosus at some future date when more material is available may show the species to be in actuality a complex of very closely related but distinct forms.
The close relationship of many of the forms of the brevisetosus complex was recognized by most earlier workers, in fact Forel (1915:220) placed his own species lujae as a subspecies of brevisetosus, a move with which Arnold (1917:397) seemed to agree. On the other hand Santschi (1916:506-508) attempted to resolve the problematical forms by placing them all as infraspecific forms of pygmaeus. The present study indicates that this was not justifiable, and of the names given as stirps, races and varieties of pygmaeus, namely difficilis, lujae, plebeja, weissi, degener, jeanneli and brevisetosus the first, fourth and last are now treated as good species whilst the remainder have been placed in the synonymy of the last. Arnold (1917:396) pointed out that the differences used to separate plebeja were slight and came within the limits of variation to be found in a single nest.
Bolton (1974) - TL 2.7 – 4.0, HL 0.76 -1.08, HW 0.68 – 0.98, CI 86 - 95, EL 0.36 – 0.48, OI 49 - 54, IOD 0.50 – 0.72, SL 0.36 – 0.50, SI 51 – 53, PW 0.54 – 0.78, AL 0.74 – 1.10, MTL 0.38 – 0.52 (20 measured).
Occipital crest absent, the vertex rounding into the occiput or separated from it by an obtuse angle. Occipital corners denticulate and a second denticle present on the occipital margin close to the corner. Sides of head behind eyes minutely denticulate in most, but in some individuals the denticles are reduced or absent. Alitrunk marginate laterally, the margination most pronounced upon the pronotum. Pronotal margins with a row of small or minute denticles, a few of which are also present upon the mesonotal and propodeal margins and may occasionally be present on the outer borders of the propodeal spines; the latter short but distinct. Dorsal alitrunk without trace of sutures. Subpetiolar process simple or with an acute posteroventral angle which may very rarely project as a short tooth. Subpostpetiolar process simple, projecting ventrally as a short blunt spine and usually about half the length of the subpetiolar process. Gaster not marginate laterally.
Dorsum of head and pronotum finely and densely reticulate-rugose with densely reticulate-punctate interspaces. Remainder of dorsal alitrunk similarly sculptured or the rugulae tending to take a longitudinal direction. More rarely the rugulae are reduced upon the mesonotum and propodeal dorsum. Dorsal surface of petiole and also usually of the postpetiole longitudinally rugose. First gastral tergite finely and densely reticulate-punctate everywhere or with sparse longitudinal rugulae present at the base of the gaster only.
Hairs on the clypeus and usually also upon the remainder of the cephalic dorsum bizarre, short and stout and either strongly clavate or stalked-suborbicular, more rarely rather spatulate. In some cases the hairs may be strongly clavate anteriorly upon the head but more or less simple posteriorly. Hairs on remainder of body numerous, short and stout but simple.
Bolton (1974) - TL 4.6 – 5.0, HL 1.04 – 1.10, HW 0.92 – 0.96, CI 87 - 90, EL 0.46, or 48 - 50, IOD 0.70 – 0.74, SL 0.48 – 0.52, SI 52 - 54, PW 0.86 – 0.90, AL 1.40 – 1.42, MTL 0.48 – 0.54 (3 measured).
As worker but with the expected modification of the alitrunk for flight. Sculpturation of mesoscutum and scutellum of fine, longitudinal rugulation and strong reticulate-puncturation. Propodeal dorsum rather more coarsely rugose than in worker, the spines shorter.
Arnold (1917) - 4 mm. Black, tibiae, tarsi, scapes, and 1st joint of the flagellum bright ochreous, the rest. of the flagellum piceous. Dull, reticulate-punctate. The head also finely reticulate-rugose, mostly longitudinally. Epinotum and nodes coarsely rugose. Abdomen moderately shining, finely and feebly reticulate. Head, seen from above and excluding the convexity of the eyes, triangular, with the apex of the triangle widely truncate, The portion of the head in front of the eyes is much shorter in this species than in durbanensis. The sides of the head without denticulations, the teeth on the posterior margin very small. The head is a little longer than wide, wider behind than the anterior margin of the thorax, but narrower than the middle of the same. Mayrian furrows much deeper than in durbanensis, and more coarsely clathrate. Dorsum of epinotum not much narrowed apically; the spines triangular, not longer than wide at the base, the brow of the declivity shallowly arcuate. The 1st node is widest in front, a trifle longer than wide, the middle of the sides slightly angular. Second node without the subacute anterior lateral angles which are seen in durbanensis. Wings hyaline, faintly tinged with yellow. Pilosity longer and less obtuse than in the worker or queen.
Holotype worker, ANGOLA: Mossamedes, Cubango-Cuito (location of type not known).
Cataulacus pygmaeus st. lujae var. plebeja Syntype workers, RHODESIA: Bulawayo, ix. 1914 (G. Arnold) (NM, Basle) [examined].
Cataulacus meduseus Holotype worker, SOUTH AFRICA: Natal, Durban, 24.i.1917 (C. P. Merve) (possibly in NMR, Bulawayo).
- Arnold, G. 1917. A monograph of the Formicidae of South Africa. Part III. Myrmicinae. Annals of the South African Museum. 14:271-402.
- Bolton, B. 1974a. A revision of the Palaeotropical arboreal ant genus Cataulacus F. Smith (Hymenoptera: Formicidae). Bull. Br. Mus. (Nat. Hist.) Entomol. 30: 1-105 (page 31, Revived status as species; senior synonym of meduseus; material of the unavailable name plebeja referred here.)
- Forel, A. 1901g. Einige neue Ameisen aus Südbrasilien, Java, Natal und Mossamedes. Mitt. Schweiz. Entomol. Ges. 10: 297-311 (page 305, worker described)
- Santschi, F. 1916b . Descriptions de fourmis nouvelles d'Afrique et d'Amérique. Ann. Soc. Entomol. Fr. 84: 497-513 (page 508, Subspecies of pygmaeus)
- Santschi, F. 1939b. Fourmis de Rhodesia et du Congo. Bull. Ann. Soc. Entomol. Belg. 79: 237-246 (page 246, Revived status as species)
- Wheeler, W. M. 1922b. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. II. The ants collected by the American Museum Congo Expedition. Bull. Am. Mus. Nat. Hist. 45: 39-269 (page 298?, Subspecies of pygmaeus)